In vitro cellular immune functions are being studied in a single masked method in patients with ocular toxoplasmosis, presumed ocular histoplasmosis, pars planitis, Behcet's disease, ocular sarcoid, and chorioretinitis of unknown origin. Crude ocular antigens as well as the purified uveitogenic soluble antigen (S-antigen) of the retina are being used in a lymphocyte microculture technique in order to evaluate the presence of cellular immune memory to ocular tissues. Immune memory is also evaluated by the production of lymphokine in a capillary migration system. A subgroup of patients have been identified as having this immunologic memory. Other studies concentrate on the presence of suppressor cell activity and functioning of macrophages in these patients. These results shed light on the basic mechanisms of uveitis and may be used as a guide for specific immunologic therapy.